Washington — On a recent afternoon, Michelle Rhee, the chancellor of the District of Columbia Public Schools, came out of a meeting to find an e-mail on her BlackBerry describing a problem at Anacostia High School. Two students had gotten into a fight while being dismissed from the cafeteria. A short time later, another student, who was smoking in a stairwell, started a small fire with his cigarette. It set off the fire alarm.

While the school evacuated to the football field, a third student ran down the hall jabbing his penknife into three kids, randomly.

“You know high school kids: When something happens it sort of causes a [chain reaction],” Ms. Rhee tells me, sounding casual, as we sit in her office. With the fire out and students milling around the 50-yard line, Rodney McBride, the Anacostia principal, calls Rhee to ask whether he should send the students home early.

Get them back in class, is her resolute response. Don’t waste the rest of the day.The incident illustrates Rhee’s no-nonsense approach to turning around one of the nation’s most troubled urban school districts.

Since she was appointed chancellor in June 2007, the young Korean-American has brought sweeping changes and a stern hand to the Washington public school system. She has fired hundreds of teachers, principals, and administrators, as well as shuttered 23 underattended schools.

At the core of her strategy is a conceptually simple but politically complex maxim: improve learning in the classroom by improving the people who hold the chalk. To do that, she advocates recruiting and retaining good teachers by paying them higher salaries – but cleaning out those who don’t perform.

Her tough approach and willingness to take on “untouchable” issues in education have earned her a reputation as a nonideological crusader who might be carving out a new model for school reform. But critics, including many teachers, see her tactics as heavy handed and capricious. Is she education’s new White Knight or just a Michelle the Knife?

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What Michelle Rhee isn’t anymore is anonymous. In the nation’s ultimate media town, she’s become something of a celebrity. On this day, she chats in a TV studio with local talk-show host Bruce DePuyt. A meteorologist at the station strolls in and laments that he didn’t bring in his copy of Time magazine that features her on the cover. He wanted her to autograph it.

“She can sign mine for you and then we can swap,” says Mr. DePuyt. Rhee smiles politely. It is the third time she has been on his show. “She’s one of my all-star guests,” DePuyt says. Rhee rolls her eyes.

The young chancellor doesn’t like to talk about her new klieg-light status or how it affects her job. “I really frankly don’t care all that much about the media,” she says. Rhee is similarly dismissive of Washington’s political rituals, saying at one point: “I’m not a politician, but I am an administrator who has to deal with politics.”

Lately, in fact, she has been embroiled in some politicking with the local teachers union over a new contract. At the heart of the dispute is the most radical element of her reform plans – performance-based salaries for teachers.

Rhee would like to see people in the classroom paid a lot more – six figure salaries in the case of some veteran teachers. It’s a prospect many teachers relish. But in exchange for the highest salaries, she would like teachers to surrender their coveted tenure protection so they can be fired if they don’t bring up test scores – something most don’t like.

As Rhee sees it, money will motivate teachers to do better and those who don’t will be (and deserve to be) let go. She believes there’s nothing wrong with the kids. “It’s the adults,” says Rhee. [Editor’s note: The original text said Rhee sees teachers, administrators, and in some cases parents as the main problem. But she never identified parents as part of the problem.]

Yet quantifying teacher performance, especially in a poor district like Washington D.C., can be problematic. Some teachers inherit a class of underachieving students. Moreover, the district has difficulties recording the most basic statistics accurately. When Rhee took charge, for instance, she didn’t have an accurate count of how many children with special needs attended her schools.

She says teachers will be evaluated through a number of lenses – student performance,classroom observations, general professionalism.

Yet not all the teachers she’s fired so far have inspired plaudits from members of the Washington Teachers’ Union and some local parents. Some fault her for acting too hastily, others for jettisoning good instructors.

“Teachers are feeling the pressure to show progress, and if they don’t show progress, they’re afraid they’re going to lose their jobs,” says Angela Morton, principal of Smothers Elementary School.

Questions persist, too, on whether Rhee can recruit enough qualified teachers to fill the vacancies that would be created by any massive turnover. “You can fire people who aren’t doing a good job, but if you then don’t have good people to put in their place, it can backfire,” says Deborah Loewenberg Ball, the dean of the School of Education at the University of Michigan who serves on an advisory board with Rhee. “I think it’s frankly more than just finding good teachers and paying them enough. You can pay people as much as you like, and they still couldn’t teach a kid to read.”

Still, many people in education circles praise Rhee for bold moves and for tackling entrenched interest groups. “I think Michelle’s strategy is the only coherent strategy to try to reform these [urban] systems,” says Rick Hess, an education expert at the American Enterprise Institute in Washington. “These are not well-run systems.”

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Rhee seems an unlikely candidate to reform public education. Before moving to Washington, she was running an education nonprofit from her home in Colorado. Rhee had never run a school district – or even attended public school much.

“I was actually surprised when I heard she was going to do Teach For America,” says Erik Rhee, her older brother. Growing up in a community of hyper-achieving Korean-Americans in Toledo, Erik says “the basic expectation was doctor, lawyer, something like that. It was generally understood that you were just going to be successful.”

After joining TFA, Rhee spent three years teaching elementary school in Baltimore. It turned out to be formative for her. “I was incredibly frustrated by what I saw happening,” she says. “I knew that I wanted to do something that would have a broader impact on public education, and I knew that teacher quality was the biggest lever to that.”

In 1997, Rhee founded her own nonprofit, The New Teacher Project, which trains people to go into urban classrooms. A decade later, D.C. Mayor Adrian Fenty, who became the governing authority over the Washington school district in June 2007, offered Rhee the opportunity of a lifetime – the chance to lead a well-funded but underperforming school system.

The statistics were stark. Washington’s eighth-grade students ranked lowest in the nation in math – only 8 percent scoring “proficient” or better in 2007. When it came to reading, the district was ranked last out of 52 jurisdictions. Still, Washington spends some $13,000 per student, among the highest rates in the country, though large amounts go to special-needs kids.

Whatever the ultimate outcome, Rhee’s education reform experiment won’t fail for lack of effort. She regularly works from 6:30 a.m. to 1 a.m., up to seven days a week. Somewhere in there Rhee spends time with her two young daughters.

After the Anacostia incident, Rhee attended a community forum where she discussed the district’s five-year plan for several hours. The next morning she was closeted with the City Council for seven hours.

Her brother knows the regimen well. He frequently gets e-mails from her after midnight. “You need to go to bed,” he will write back. Her usual response: “Yeah, soon.”